Smith studies the metabolism in plants of starch and sucrose – the carbohydrate products of photosynthesis that fuel plant growth. Her research has uncovered metabolic pathways responsible for the synthesis and degradation of starch granules in plants. She showed that these processes in leaves are subject to complex control by the circadian clock over the day-night cycle, ensuring the availability of carbohydrate to fuel metabolism during the night. Her focus is now on the mechanisms underlying this control, and the way in which carbohydrate availability is integrated with other sources of information to determine rates and patterns of growth and development in plants.[3][6][7]

Smith uses information from her fundamental studies to examine starch turnover in crop plants. Current research on starch synthesis in cereal grains has the potential to increase crop yield, and to change important functional and nutritional properties of flour.[3]